ARM: dts: at91: add a dts and dtsi file for kizbox2 based boards

ARM: dts: at91: add a dts and dtsi file for kizbox2 based boards

There are several boards available depending on the PCB
(3 antennas support and several revison). Add a dtsi file to share
common binding between all kizbox2 boards. This patch also add support
for the kizbox2-2 variant.

Signed-off-by: Kévin RAYMOND <k.raymond@overkiz.com>
Signed-off-by: Mickael GARDET <m.gardet@overkiz.com>
Signed-off-by: Kamel Bouhara <kamel.bouhara@bootlin.com>
Link: https://lore.kernel.org/r/20191105212234.22999-2-kamel.bouhara@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>